Communication systems may be represented in terms of a transmitter 100 and receiver 104, separated by a channel 102, as shown in FIG. 1. The transmitter transforms the data into a signal suitable for transmission over the channel. For the purposes of determining the transmitted data, the goal of the receiver 104 is to remove the effects of the channel distortions from the signal and to obtain an estimate of the data. The receiver 104 may also provide other information, such as a measure of received power, received signal samples and/or an estimate of the channel.
The channel 102 represents the effects induced by the communications channel. The channel 102 may distort the transmitted signal in some way. Channel distortions may include amplitude distortions, frequency offsets, phase offsets, Doppler effects, distortions resulting from multipath channels, additive noise or interference.
Spatial parameters pertaining to the transmitter 102 and/or receiver 104 devices may be known. Such parameters may include spatial coordinates, velocity, and acceleration. For example, the devices may be positioned at known fixed locations. Spatial parameters may also be obtained from a Global Positioning System (GPS) receiver or similar device. Furthermore, spatial information relating to the transmitter 102 may be passed to the receiver 104 within the transmitted data content. An example of such a case occurs in Dedicated Short Range Communications (DSRC) systems, where transmitted data may include position, speed, acceleration and heading information, as described in SAE International, “Dedicated Short Range Communications (DSRC) Message Set Dictionary,” J2735, December 2006. Spatial information pertaining to system components, and receiver information such as an estimate of the channel, may be used to detect, track and characterise objects in the environment surrounding a wireless communications system, as described in co-pending international patent application PCT/AU2010/000768 filed on 28 Jun. 2010, the contents of which are incorporated herein by reference.
Reference to any prior art in the specification is not, and should not be taken as, an acknowledgement or any form of suggestion that this prior art forms part of the common general knowledge in any other jurisdiction or that this prior art could reasonably be expected to be ascertained, understood and regarded as relevant by a person skilled in the art.